Separation of isopropyl ether from acetone by extractive distillation

ABSTRACT

Isopropyl ether cannot be completely removed from isopropyl ether-acetone mixtures by distillation because of the presence of the minimum binary azeotrope. Isopropyl ether can be readily removed from mixtures containing it and acetone by using extractive distillation in which the extractive distillation agent is a higher boiling oxygenated or nitrogenous organic compound or a mixture of these. Typical examples of effective agents are: dimethylsulfoxide; sulfolane and propylene glycol; glycerine, ethylene glycol and adiponitrile.

FIELD OF THE INVENTION

This invention relates to a method for separating isopropyl ether fromacetone using certain higher boiling liquids as the extractive agent inextractive distillation.

DESCRIPTION OF PRIOR ART

Extractive distillation is the method of separating close boilingcompounds or azeotropes by carrying out the distillation in a multiplaterectification column in the presence of an added liquid or liquidmixture, said liquid(s) having a boiling point higher than the compoundsbeing separated. The extractive agent is introduced near the top of thecolumn and flows downward until it reaches the stillpot or reboiler. Itspresence on each plate of the rectification column alters the relativevolatility of the close boiling compounds in a direction to make theseparation on each plate greater and thus require either fewer plates toeffect the same preparation or make possible a greater degree ofseparation with the same number of plates. When the compounds to beseparated normally form an azeotrope, the proper agents will cause themto boil separately during extractive distillation and thus make possiblea separation in a rectification column that cannot be done at all whenno agent is present. The extractive agent should boil higher than any ofthe close boiling liquids being separated and not form minimumazeotropes with them. Usually the extractive agent is introduced a fewplates from the top of the column to insure that none of the extractiveagent is carried over with the lowest boiling component. This usuallyrequires that the extractive agent boil twenty Centigrade degrees ormore higher than the lowest boiling component.

At the bottom of a continuous column, the less volatile components ofthe close boiling mixtures and the extractive agent are continuouslyremoved from the column. The usual methods of separation of these twocomponents are the use of another rectification column, cooling andphase separation, or solvent extraction.

One of the commercially important ways to manufacture acetone is by thecatalytic dehydrogenation of isopropanol. Since the acetone (b.p.=56.15°C.) does not form an azeotrope with isopropanol (b.p.=82.4° C.), theacetone is relatively easy to separate from the unreacted isopropanol byrectification. However a concurrent reaction takes place in which someof the isopropanol dehydrates to form isopropyl ether (b.p.=69° C.).Acetone and isopropyl ether form a minimum azeotrope boiling at 54.2° C.at one Atm. pressure and containing 61 wt.% acetone, 39 wt. % isopropylether. It is therefore impossible to produce pure acetone fromacetone-isopropyl ether mixtures by rectification because the lowerboiling azeotrope will always come off overhead as the initial product.Any mixture of acetone and isopropyl ether subjected to rectification atone atmosphere pressure will produce an overhead product boiling at54.2° C. and containing 61% acetone, 39% isopropyl ether. Extractivedistillation would be an attractive method of effecting the separationof acetone from isopropyl ether if agents can be found that (1) willbreak the acetone-isopropyl ether azeotrope and (2) are easy to recoverfrom the acetone, that is, form no azeotrope with acetone and boilsufficiently above acetone to make the separation by rectificationpossible with only a few theoretical plates.

Extractive distillation typically requires the addition of an equalamount to twice as much extractive agent as the acetone-isopropyl etheron each plate in the rectification column. The extractive agent shouldbe heated to about the same temperature as the plate into which it isintroduced. Thus extractive distillation imposes an additional heatrequirement on the column as well as somewhat larger plates. Howeverthis is less than the increase occasioned by the additional agentsrequired in azeotropic distillation.

Another consideration in the selection of the extractive distillationagent is its recovery from the bottoms product. The usual method is byrectification in another column. In order to keep the cost of thisoperation to a minimum, an appreciable boiling point difference betweenthe compound being separated and the extractive agent is desirable. Werecommend twenty Centigrade degrees or more difference. It is alsodesirable that the extractive agent be miscible with acetone otherwiseit will form a two phase azeotrope with the acetone in the recoverycolumn and some other method of separation will have to be employed.

The breaking of an azeotrope by extractive distillation is a newconcept. The closest application of this concept might be the breakingof the ethanol-water azeotrope. J. Schneible, (U.S. Pat. No. 1,469,447)used glycerol; P. V. Smith & C. S. Carlson (U.S. Pat. No. 2,559,519)employed ethoxyethanol and butoxyethanol for this purpose and W. E.Catterall, (U.S. Pat. No. 2,591,672) reported gasoline as beingeffective. These are dehydrations and operate more conventionally as asolvent extraction process rather than an extractive distillation.

OBJECTIVE OF THE INVENTION

The object of this invention is to provide a process or method ofextractive distillation that will enhance the relative volatility ofisopropyl ether from acetone in their separation in a rectificationcolumn. It is a further object of this invention to identify suitableextractive distillation agents which will eliminte the isopropylether-acetone binary azeotrope and make possible the production of pureisopropyl ether and acetone by rectification. It is a further object ofthis invention to identify organic compounds which, in addition to theabove constraints, are stable, can be separated from acetone byrectification with relatively few plates and can be recycled to theextractive distillation column and reused with little decomposition.

SUMMARY OF THE INVENTION

The objects of this invention are provided by a process for separatingisopropyl ether from acetone which entails the use of certainoxygenated, nitrogenous and/or sulfur containing organic compounds asthe agent in extractive distillation.

DETAILED ELABORATION OF THE INVENTION

We have discovered that certain oxygenated, nitrogenous and/or sulfurcontaining organic compounds, some individually but principally asmixtures, will effectively negate the isopropyl ether-acetone azeotropeand permit the separation of pure isopropyl ether from acetone byrectification when employed as the agent in extractive distillation.Table I lists the compounds, mixtures and approximate proportions thatwe have found to be exceptionally effective. Table II lists thecompounds, mixtures and approximate proportions that are successful butdo not give quite as high a relative volatility as that obtained fromthose in Table I. Table III lists those compounds and mixtures which wefound to be relatively unsuccessful. The data in Tables I, II and IIIwere obtained in a vapor-liquid equilibrium still. In each case, thestarting material was the isopropyl ether-acetone azeotrope. The ratiosare the parts by weight of extractive agent used per part of isopropylether-acetone azeotrope. The relative volatilities are listed for eachof the two ratios employed.

The compounds that are effective as extractive distillation agents whenused alone are ethylene glycol, propylene glycol, 1,3-butanediol,1,4-butanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol,tetraethylene glycol, glycerine, 3-chloro-1,2-propanediol,dimethylsulfoxide, sulfolane, dimethylformamide and adiponitrile. Thecompounds which are effective when used in mixtures of two or morecomponents are diethylene glycol, dipropylene glycol, 1,5-pentanediol,hexylene glycol, polyethylene glycol, diisooctyl phthalate, benzylalcohol, phenol and nitrobenzene.

The ratios shown in Tables I, II and III are the parts by weight ofextractive agent used per part of isopropyl ether-acetone azeotrope. Thetwo relative volatilities correspond to the two different ratios. Forexample in Table I, one part of ethylene glycol with one part ofisopropyl ether-acetone azeotrope gives a relative volatility of 3.80,6/5 parts of ethylene glycol gives 5.62. One half part of glycerinemixed with one half part of sulfolane with one part of isopropylether-acetone azeotrope gives a relative volatility of 3.85, 3/5 partsof glycerine plus 3/5 parts of sulfolane gives 4.36. One third parts ofglycerine plus 1/3 parts of ethylene glycol plus 1/3 parts of DMSO mixedwith one part of isopropyl ether-acetone azeotrope gives a relativevolatility of 4.82, and 2/5 parts, these three give 4.05.

In every example in Tables I, II and III the starting material is theisopropyl ether-acetone azeotrope which possesses a relative volatilityof 1.00.

Table III lists combinations of some of the same compounds presented inTables I and II which failed to give relative volatilities as high as2.0. It also lists a few combinations that give relative volatilities ofless than 1.0. This indicates the importance of employing thesecompounds in the proper ratio and combination.

Several of the compounds and mixtures listed in Tables I and II andwhose relative volatility had been determined in the vapor-liquidequilibrium still, were then evaluated in a glass perforated platerectification column possessing 4.5 theoretical plates. The results arelisted in Table IV. The isopropyl ether-acetone mixture studiedcontained 8% isopropyl ether, 92% acetone. The isopropyl ether-acetoneazeotrope contains 39 wt.% isopropyl ether, 61 wt.% acetone. What atruly remarkable here is that isopropyl ether, the less volatilecomponent, will come off as overhead product. In every case the feed orbottoms composition contained less than 39% isopropyl ether and in everycase the overhead is richer than 39% isopropyl ether. Without theextractive agent, the overhead would be the azeotrope, 39% isopropylether. This proves that the extractive agent is negating the azeotropeand makes the rectification proceed as if the azeotrope no longerexisted and brings the less volatile component, isopropyl ether, out asthe overhead. It is our belief that this is the first time that this hasbeen accomplished for any azeotrope.

The data in Table IV was obtained in the following manner. The chargedesignated "blank" was 8% isopropyl ether, 92% acetone and after 1.5hours operation in the 4.5 theoretical plate column, the relativevolatility of the separation between the isopropyl ether-acetoneazeotrope and acetone was 1.42. The remaining data is for the extractivedistillation agents designated. Here we not only have negated theazeotrope but the isopropyl ether has become the more volatilecomponent. The temperature of the overhead approaches 63° C., theboiling point of pure isopropyl ether at 630 mm.Hg and the acetone goesto the stillpot with the extractive distillation agent. The designation"R" by the extractive distillation agent means that the same materialwas recovered and re-used to show its stability in repeated operation.When the acetone--extractive distillation agent mixture taken from thestillpot is redistilled, acetone comes off overhead in the usual way atits normal boiling point, 56° C.

                                      TABLE I                                     __________________________________________________________________________    Extractive Distillation Agents Which Are Exceptionally Effective              In Separating Acetone from Isopropyl Ether                                                                      Relative                                    Compounds                  Ratios Volatilities                                __________________________________________________________________________    Ethylene glycol            1  6/5 3.80                                                                             5.62                                     Dimethylsulfoxide (DMSO)   "  "   3.78                                                                             4.92                                     1,6-Hexanediol             "  "   3.82                                                                             4.45                                     Adiponitrile               "  "   3.82                                                                             4.07                                     Sulfolane                  "  "   3.09                                                                             3.80                                     Glycerine                  "      3.13                                                                             --                                       Glycerine, DMSO               (3/5).sup.2                                                                       -- 3.82                                     Glycerine, Dimethylformamide (DMFA)                                                                      (1/2).sup.2                                                                      "   2.91                                                                             3.63                                     Glycerine, Sulfolane       "  "   3.85                                                                             4.36                                     Glycerine, 1,6-Hexanediol  "  "   3.26                                                                             4.42                                     Glycerine, 3-Chloro-1,2-propanediol                                                                      "  "   3.57                                                                             --                                       Ethylene glycol, DMSO      "  "   3.14                                                                             3.31                                     Ethylene glycol, Sulfolane "  "   4.01                                                                             4.57                                     Ethylene glycol, 1,4-Butanediol                                                                          "  "   3.26                                                                             3.77                                     Ethylene glycol, 3-Chloro-1,2-propanediol                                                                "  "   3.53                                                                             4.29                                     DMSO, Adiponitrile         "  "   3.71                                                                             3.81                                     DMSO, 1,4-Butanediol       "  "   3.08                                                                             3.50                                     DMSO, 3-Chloro-1,2-propanediol                                                                           "  "   2.74                                                                             4.73                                     Sulfolane, Adiponitrile    "  "   3.98                                                                             3.08                                     Sulfolane, DMSO            "  "   3.57                                                                             4.10                                     Sulfolane, Propylene glycol                                                                              "  "   3.07                                                                             3.16                                     Sulfolane, Triethylene glycol                                                                            "  "   3.07                                                                             3.10                                     Sulfolane, 1,6-Hexanediol  "  "   3.56                                                                             4.34                                     Sulfolane, 3-Chloro-1,2-propanediol                                                                      "  "   3.07                                                                             3.29                                     Glycerine, Ethylene glycol, DMSO                                                                         (1/3).sup.3                                                                      (2/5).sup.3                                                                       4.82                                                                             4.05                                     Glycerine, Ethylene glycol, Dipropylene glycol                                                           "  "   2.59                                                                             3.69                                     Glycerine, Ethylene glycol, Adiponitrile                                                                 "  "   4.04                                                                             4.60                                     Glycerine, Ethylene glycol, Sulfolane                                                                    "  "   3.60                                                                             3.06                                     Glycerine, DMSO, Propylene glycol                                                                        "  "   2.93                                                                             3.59                                     Glycerine, DMSO, 1,4-Butanediol                                                                          "  "   3.46                                                                             3.40                                     Glycerine, DMSO, Tetraethylene glycol                                                                    "  "   3.70                                                                             3.98                                     Glycerine, DMSO, Polyethylene glycol 300                                                                 "  "   3.60                                                                             4.36                                     Glycerine, DMSO, 3-Chloro-1,2-propanediol                                                                "  "   3.20                                                                             3.64                                     Glycerine, DMSO, Diisooctyl phthalate                                                                    "  "   3.95                                                                             3.13                                     Glycerine, DMSO, Adiponitrile                                                                            "  "   4.19                                                                             4.00                                     Glycerine, DMSO, Sulfolane "  "   3.84                                                                             3.79                                     Ethylene glycol, DMSO, Propylene glycol                                                                  "  "   4.03                                                                             3.66                                     Ethylene glycol, DMSO, 1,4-Butanediol                                                                    "  "   2.98                                                                             3.47                                     Ethylene glycol, DMSO, 1,5-Pentanediol                                                                   "  "   3.12                                                                             3.42                                     Ethylene glycol, DMSO, Diethylene glycol                                                                 "  "   3.21                                                                             3.34                                     Ethylene glycol, DMSO, Triethylene glycol                                                                "  "   3.04                                                                             3.83                                     Ethylene glycol, DMSO, Tetraethylene glycol                                                              "  "   3.30                                                                             3.54                                     Ethylene glycol, DMSO, 3-Chloro-1,2-propanediol                                                          "  "   3.01                                                                             3.87                                     Ethylene glycol, DMSO, Adiponitrile                                                                      "  "   3.80                                                                             4.39                                     Ethylene glycol, DMSO, Sulfolane                                                                         "  "   4.23                                                                             6.39                                     DMSO, Sulfolane, Propylene glycol                                                                        "  "   3.17                                                                             3.53                                     DMSO, Sulfolane, 1,4-Butanediol                                                                          "  "   4.88                                                                             --                                       DMSO, Sulfolane, Adiponitrile                                                                            "  "   3.46                                                                             3.32                                     DMSO, Sulfolane, Adiponitrile, Glycerine                                                                 (1/4).sup.4                                                                      (1/3).sup.4                                                                       4.38                                                                             4.32                                     DMSO, Sulfolane, Adiponitrile, Ethylene glycol                                                           "  "   4.53                                                                             5.04                                     DMSO, Sulfolane, Adiponitrile, Propylene glycol                                                          "  "   3.60                                                                             3.80                                     DMSO, Sulfolane, Adiponitrile, 1,5-Pentanediol                                                           "  "   2.96                                                                             3.27                                     DMSO, Sulfolane, Adiponitrile, 1,6-Hexanediol                                                            "  "   3.01                                                                             3.10                                     DMSO, Sulfolane, Adiponitrile, Diethylene glycol                                                         "  "   3.24                                                                             3.28                                     DMSO, Sulfolane, Adiponitrile, Triethylene glycol                                                        "  "   3.57                                                                             3.55                                     DMSO, Sulfolane, Adiponitrile, Tetraethylene glycol                                                      "  "   3.27                                                                             3.20                                     DMSO, Sulfolane, Adiponitrile, Dipropylene glycol                                                        "  "   2.87                                                                             3.17                                     DMSO, Sulfolane, Adiponitrile, 3-Chloro-1,2-propanediol                                                  "  "   3.16                                                                             3.38                                     __________________________________________________________________________

                                      TABLE II                                    __________________________________________________________________________    Extractive Distillation Agents Which Are Effective In Separating              Acetone From Isopropyl Ether                                                                                  Relative                                      Compounds                Ratios Volatilities                                  __________________________________________________________________________    Propylene glycol         1  (6/5)                                                                             2.10                                                                             2.76                                       1,3-Butanediol           "  "   2.55                                                                             2.45                                       1,4-Butanediol           "  "   2.23                                                                             2.20                                       Diethylene glycol        "  "   2.38                                                                             2.15                                       Triethylene glycol       "  "   2.50                                                                             1.83                                       Tetraethylene glycol     "  "   1.97                                                                             2.51                                       3-Chloro-1,2-propanediol "  "   2.62                                                                             3.13                                       Dimethylformamide (DMFA) "  "   2.05                                                                             2.08                                       Glycerine, Propylene glycol                                                                            (1/2).sup.2                                                                      (3/5).sup.2                                                                       2.32                                                                             3.72                                       Glycerine, 1,5-Pentanediol                                                                             "  "   2.01                                                                             2.62                                       Ethylene glycol, Tetraethylene glycol                                                                  "  "   2.67                                                                             2.77                                       DMSO, Propylene glycol   "  "   2.68                                                                             2.74                                       DMSO, 1,3-Butanediol     "  "   2.76                                                                             2.38                                       DMSO, 1,5-Pentanediol    "  "   2.37                                                                             2.70                                       DMSO, 1,6-Hexanediol     "  "   1.74                                                                             2.51                                       DMSO, Hexylene glycol    "  "   2.01                                                                             2.04                                       DMSO, Diethylene glycol  "  "   2.41                                                                             3.23                                       DMSO, Triethylene glycol "  "   2.57                                                                             2.86                                       DMSO, Tetraethylene glycol                                                                             "  "   2.56                                                                             2.78                                       DMSO, Dipropylene glycol "  "   2.36                                                                             2.45                                       DMSO, 3-Chloro-1,2-propanediol                                                                         "  "   2.52                                                                             2.87                                       DMSO, Benzyl alcohol     "  "   2.19                                                                             3.00                                       Sulfolane, 1,3-Butanediol                                                                              "  "   2.79                                                                             2.99                                       Sulfolane, 1,4-Butanediol                                                                              "  "   2.83                                                                             3.05                                       Sulfolane, 1,5-Pentanediol                                                                             "  "   2.56                                                                             2.74                                       Sulfolane, Diethylene glycol                                                                           "  "   2.93                                                                             2.82                                       Sulfolane, Tetraethylene glycol                                                                        "  "   2.87                                                                             2.93                                       Sulfolane, Dipropylene glycol                                                                          "  "   2.47                                                                             2.85                                       Sulfolane, Phenol        "  "   2.32                                                                             2.63                                       DMFA, 1,3-Butanediol     "  "   2.52                                                                             2.55                                       DMFA, 3-Chloro-1,2-propanediol                                                                         "  "   2.29                                                                             2.38                                       Sulfolane, 1,6-Hexanediol                                                                              "  "   2.51                                                                             2.83                                       Sulfolane, Hexylene glycol                                                                             "  "   2.11                                                                             2.16                                       Glycerine, Ethylene glycol, Propylene glycol                                                           (1/3).sup.3                                                                      (2/5).sup.3                                                                       2.65                                                                             2.96                                       Glycerine, Ethylene glycol, 1,5-Pentanediol                                                            "  "   2.26                                                                             3.52                                       Glycerine, Ethylene glycol, Diethylene glycol                                                          "  "   2.03                                                                             3.35                                       Glycerine, Ethylene glycol, Triethylene glycol                                                         "  "   2.32                                                                             3.76                                       Glycerine, Ethylene glycol, Formamide                                                                  "  "   2.48                                                                             2.98                                       Glycerine, DMSO, Propylene glycol                                                                      "  "   2.97                                                                             2.13                                       Glycerine, DMSO, 1,3-Butanediol                                                                        "  "   2.95                                                                             1.95                                       Glycerine, DMSO, 1,4-Butanediol                                                                        "  "   2.84                                                                             3.05                                       Glycerine, DMSO, 1,5-Pentanediol                                                                       "  "   2.56                                                                             3.40                                       Glycerine, DMSO, 1,6-Hexanediol                                                                        "  "   2.37                                                                             2.93                                       Glycerine, DMSO, Hexylene glycol                                                                       "  "   2.44                                                                             2.70                                       Glycerine, DMSO, Triethylene glycol                                                                    "  "   2.33                                                                             2.00                                       Glycerine, DMSO, Diethylene glycol                                                                     "  "   2.60                                                                             3.37                                       Glycerine, DMSO, Dipropylene glycol                                                                    "  "   2.40                                                                             2.76                                       Glycerine, DMSO, 3-Chloro-1,2-propanediol                                                              "  "   2.26                                                                             2.87                                       Glycerine, DMSO, Nitrobenzene                                                                          "  "   3.36                                                                             2.11                                       Glycerine, DMFA, 1,5-Pentanediol                                                                       "  "   2.21                                                                             3.25                                       Ethylene glycol, DMSO, 1,3-Butanediol                                                                  "  "   2.60                                                                             3.38                                       Ethylene glycol, DMSO, 1,6-Hexanediol                                                                  "  "   2.33                                                                             3.09                                       Ethylene glycol, DMSO, Hexylene glycol                                                                 "  "   2.42                                                                             2.65                                       Ethylene glycol, DMSO, Dipropylene glycol                                                              "  "   2.45                                                                             3.18                                       Ethylene glycol, DMSO, Polyethylene glycol 300                                                         "  "   2.73                                                                             2.90                                       Propylene glycol, DMSO, 3-Chloro-1,2-propanediol                                                       "  "   2.38                                                                             2.19                                       DMSO, Sulfolane, Adiponitrile, 1,4-Butanediol                                                          (1/4).sup.4                                                                      (1/3).sup.4                                                                       2.92                                                                             2.82                                       DMSO, Sulfolane, Adiponitrile, Hexylene glycol                                                         "  "   2.32                                                                             2.49                                       __________________________________________________________________________

                  TABLE III                                                       ______________________________________                                        Extractive Distillation Agents Which Are Relatively Ineffective               In Separating Acetone From Isopropyl Ether                                                                   Relative                                       Compounds           Ratios     Volatilities                                   ______________________________________                                        1,5-Pentanediol     1      6/5     1.82 1.79                                  Hexylene glycol     "      "       1.24 1.38                                  Glycerine, Ethylene glycol                                                                        (1/2).sup.2                                                                          (3/5).sup.2                                                                           0.90 0.73                                  Glycerine, 1,4-Butanediol                                                                         "      "       1.91 1.52                                  Glycerine, 1,5-Pentanediol                                                                        "      "       2.31 1.52                                  Glycerine, Tetraethylene glycol                                                                   "      "       2.73 1.18                                  DMSO, Diisooctyl phthalate                                                                        "      "       1.61 1.80                                  1,5-Pentanediol, Tetraethylene glycol                                                             "      "       2.12 1.84                                  3-Chloro-1,2-propanediol,                                                                         "      "       1.43 1.89                                  Nitrobenzene                                                                  Glycerine, Ethylene glycol,                                                                       (1/3).sup.3                                                                          (2/5).sup.3                                                                           2.26 1.25                                  1,4-Butanediol                                                                Glycerine, Ethylene glycol,                                                                       "      "       1.96 0.94                                  Diisobutyl phthalate                                                          ______________________________________                                    

                                      TABLE IV                                    __________________________________________________________________________    Data From Rune Made in Rectification Column.                                                  Overhead                                                                            Stillpot Temp., °C.                                                                Relative                                                                           Time to Reach                          Compounds       Temp., °C.                                                                   at Start After 1.5 hrs.                                                                   Volatility                                                                         Equil., hrs.                           __________________________________________________________________________    Blank           49    53    53    1.42 0.5                                    DMSO            63    54    86    5.97 1                                      DMSO (R)        63    54    84    5.90 1                                      Adiponitrile    62    54    85    5.43 1                                      Sulfolane       62    54    84    4.52 1                                      Sulfolane (R)   59    55    84    4.43 1                                      Glycerine       49    53    69    1.67 0.5                                    Ethylene glycol 56    54    77    2.72 1                                      DMSO + Adiponitrile                                                                           62    54    87    4.89 1                                      DMSO (R) + Sulfolane (R)                                                                      62    54    84    4.62 1                                      Sulfolane (R) + Adiponitrile (R)                                                              61    55    82    4.27 1                                      DMSO + Glycerine                                                                              57    56    70    2.89 1                                      Sulfolane + Glycerine                                                                         56    55    76    2.74 1                                      DMSO (R) + Sulfolane (R) +                                                                    61    55    83    4.06 1                                      Adiponitrile (R)                                                              DMSO (R) + Sulfolane (R) +                                                                    60    55    76    3.19 1                                      Glycerine (R)                                                                 __________________________________________________________________________

THE USEFULNESS OF THE INVENTION

The usefulness or utility of this invention can be demonstrated byreferring to the data presented in Tables I, II, III and IV. All of thesuccessful extractive distillation agents show that isopropyl ether canbe removed from its binary minimum azeotrope with acetone by means ofdistillation in a rectification column and that the ease of separationas measured by relative volatility is considerable. Without theseextractive distillation agents, no improvement above the azeotropecomposition will occur in the rectification column. The data also showthat the most attractive agents will operate at a boilup rate low enoughto make this a useful and efficient method of recovering high purityisopropyl ether from any mixture with acetone including the minimumazeotrope. The stability of the compounds used and the boiling pointdifference is such that complete recovery and recycle is obtainable by asimple distillation and the amount required for make-up is small.

WORKING EXAMPLES EXAMPLE 1

The isopropyl ether-acetone azeotrope is 39% isopropyl ether, 61%acetone. Fifty grams of the isopropyl ether-acetone azeotrope and fiftygrams of sulfolane were charged to an Othmer type glass vapor-liquidequilibrium still and refluxed for ten hours. Analysis of the vapor andliquid by gas chromatography gave vapor 71.4% isopropyl ether, 28.6%acetone; liquid of 44.7% isopropyl ether, 55.3% acetone. This indicatesa relative volatility of of 3.09. Ten grams of sulfolane were added andrefluxing continued for another eleven hours. Analysis indicated a vaporcomposition of 71.1% isopropyl ether, 28.9% acetone, a liquidcomposition of 39.2% isopropyl ether, 60.8% acetone which is a relativevolatility of 3.80.

EXAMPLE 2

Fifty grams of isopropyl ether-acetone azeotrope, 25 grams of sulfolaneand 25 grams of DMSO were charged to the vapor-liquid equilibrium stilland refluxed for ten hours. Analysis indicated a vapor composition of70.5% isopropyl ether, 29.5% acetone, a liquid composition of 42%isopropyl ether, 58% acetone which is a relative volatility of 3.57.Five grams of sulfolane and five grams of DMSO were added and refluxingcontinued for another twelve hours. Analysis indicated a vaporcomposition of 71.7% isopropyl ether, 28.3% acetone, a liquidcomposition of 38.2% isopropyl ether, 61.8% acetone which is a relativevolatility of 4.10.

EXAMPLE 3

Fifty grams of the isopropyl ether-acetone azeotrope, 17 grams ofglycerine, 17 grams of DMSO and 17 grams of sulfolane were charged tothe vapor-liquid equilibrium still and refluxed for ten hours. Analysisindicated a vapor composition of 69.9% isopropyl ether, 30.1% acetone, aliquid composition of 37.7% isopropyl ether, 62.3% acetone which is arelative volatility of 3.84. Three grams each of glycerine, DMSO andsulfolane were added and refluxing continued for another twelve hours.Analysis indicated a vapor composition of 69.5% isopropyl ether, 30.5%acetone, a liquid composition of 37.5% isopropyl ether, 62.5% acetonewhich is a relative volatility of 3.79.

EXAMPLE 4

A glass perforated plate rectification column was calibrated withethylbenzene and p-xylene which possesses a relative volatility of 1.06and found to have 4.5 theoretical plates. A solution of 460 grams ofacetone and 40 grams of isopropyl ether was placed in the stillpot andheated. When refluxing began, an extractive agent containing puresulfolane was pumped into the column at a rate of 20 ml/min. Thetemperature of the extractive agent as it entered the column was 52° C.After establishing the feed rate of the extractive agent, the heat inputto the isopropyl ether and acetone in the stillpot was adjusted to givea total reflux rate of 10-20 ml/min. After one-half hour of operation,overhead and bottoms samples of approximately two ml. were collected andanalysed using gas chromatography. The overhead analysis was 91.25%isopropyl ether, 8.75% acetone. The bottoms analysis was 4.68% isopropylether, 95.32% acetone. Using these compositions in the Fenske equation,with the number of theoretical plates in the column being 4.5, gave anaverage relative volatility of 3.29 for each theoretical plate. Afterone hour of total operating time, the overhead and bottoms samples wereagain taken and analysed. The overhead composition was 96.68% isopropylether, 3.32% acetone and the bottoms composition was 3.15% isopropylether, 96.85% acetone. This gave an average relative volatility of 4.53for each theoretical plate. After 1.5 hours of total operating time, theoverhead and bottoms samples were again taken and analysed. The overheadcomposition was 96.46% isopropyl ether, 3.54% acetone and the bottomscomposition was 2.97% isopropyl ether, 97.03% acetone. This gave anaverage relative volatility of 4.52 for each theoretical plate.

EXAMPLE 5

A solution of 460 grams of acetone and 40 grams of isopropyl ether wasplaced in the stillpot of the same column used in Example 4 and heatapplied. When refluxing began, an extractive agent of 50% DMSO and 50%sulfolane was fed into the top of the column at a feed rate of 20ml/min. and a temperature of 52° C. After establishing the feed rate ofthe extractive agent, the heat input to the isopropyl ether and acetonein the stillpot was adjusted to give a total reflux rate of 10-20ml/min. Having established the reflux rate, the column was allowed tooperate for one-half hour. After one-half hour of steady operation,overhead and bottoms samples of approximately two ml. were collected andanalysed using gas chromatography. The overhead analysis was 89.07%isopropyl ether, 10.93% acetone; the bottoms analysis was 4.65%isopropyl ether, 95.35% acetone. Using these compositions in the Fenskeequation with the the number of theoretical plates of the column being4.5, gave an average relative volatility of 3.12 for each theoreticalplate. After one hour of total operation, the overhead composition was96.95% isopropyl ether, 3.05% acetone and the bottoms composition was3.13% isopropyl ether, 96.87% acetone. This gave an average relativevolatility of 4.62 for each theoretical plate. After 1.5 hours of totaloperation, the overhead composition was 97.96% isopropyl ether, 2.04%acetone and the bottoms composition was 3.5% isopropyl ether, 96.5%acetone. This gave an average relative volatility of 4.94 for eachtheoretical plate.

We have shown that by the use of the proper compound or combination ofcompounds as agents isopropyl ether can be effectively removed from itsmixture with acetone in any proportion including the minimum azeotrope.

The nature of the present invention having been described, what we wishto claim as new and useful and secure by Letters Patent is:
 1. A methodfor recovering isopropyl ether from a mixture of isopropyl ether andacetone which comprises distilling a mixture of isopropyl ether andacetone in a rectification column in the presence of an effective amountof an extractive agent, recovering essentially pure isopropyl ether asoverhead product and obtaining the extractive agent and acetone from thestillpot or reboiler, the extractive agent includes polyols.
 2. Themethod of claim 1 in which the extractive agent comprises ethyleneglycol.
 3. The method of claim 1 in which the extractive agent comprisespropylene glycol.
 4. The method of claim 1 in which the extractive agentcomprises glycerine.
 5. The method of claim 1 in which the extractiveagent comprises 1,3-butanediol.
 6. The method of claim 1 in which theextractive agent comprises 1,4-butanediol.
 7. The method of claim 1 inwhich the extractive agent comprises 1,6-hexanediol.
 8. The method ofclaim 1 in which the extractive agent comprises diethylene glycol. 9.The method of claim 1 in which the extractive agent comprisestriethylene glycol.
 10. The method of claim 1 in which the extractiveagent comprises tetraethylene glycol.
 11. The method of claim 1 in whichthe extractive agent comprises 3-chloro-1,2-propanediol.
 12. The methodof claim 1 in which the extractive agent comprises a mixture of ethyleneglycol and one or more of the following: dimethylsulfoxide, sulfolane,1,3-butanediol, 1,4-butanediol, 3-chloro-1,2-propanediol, propyleneglycol, 1,5-pentanediol, diethylene glycol, triethylene glycol,tetraethylene glycol, adiponitrile, hexylene glycol, dipropylene glycol,polyethylene glycol.
 13. The method of claim 1 in which the extractiveagent comprises a mixture of glycerine and one or more of the following:sulfolane, dimethylsulfoxide, dimethylformamide, ethylene glycol,propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol,1,6-hexanediol, hexylene glycol, diethylene glycol, triethylene glycol,tetraethylene glycol, dipropylene glycol, polyethylene glycol,3-chloro-1,2-propanediol, adiponitrile, diisooctyl phthalate, formamide,nitrobenzene.